Benign prostatic hyperplasia (BPH) is the main cause of lower urinary tract symptoms in older men. Finasteride, a prostate 5α-reductase inhibitor, is a therapeutic agent widely used for BPH. D- 004, a lipid extract from Roystonea regia fruits, prevents prostate hyperplasia (PH) induced with testosterone (T), not with dyhidrotestosterone (DHT) in rodents. This study was undertaken to evaluate whether the combined therapy with D-004 + finasteride could induce additional benefits on T-induce PH in rats compared with the respective monotherapies. Firstly, we assessed the dose-effect relation of finasteride on this model, for which rats were randomly distributed in six groups (10 rats/group). A negative control group injected with soy oil s.c, and five groups injected with T (3 mg/kg, s.c): a positive control treated only with the vehicle and four groups treated with finasteride (0.5, 1, 3, and 10 mg/kg). Later on, the putative interaction between D-004 and finasteride was investigated, for which rats were randomly allocated in five groups (10 rats/group): a negative control, treated with the vehicle, and four treated with T: a positive control and three groups treated with finasteride (0.5 mg/kg), D-004 (200 mg/kg) and combined therapy D-004 200 mg/kg + finasteride 0.5 mg/kg, respectively. All treatments were administered for 14 days. Bodyweight was controlled weekly. At study completion, prostates were weighed. Finasteride (0.5 - 10 mg/kg) significantly and doses dependently inhibited prostate increase, inhibitions ranging from 45.8% to 100%. Combined therapy inhibited prostate enlargement in 63.7%, the reduction on prostate weight being significant versus the positive control and each monotherapy, which at the doses tested inhibited prostate weight increase by 32.9% (D-004 200 mg/kg) and 30.6% (finasteride 0.5 mg/kg). In conclusion, combined therapy with minimal effective doses of both D-004 and finasteride in this model induced additional benefits in preventing T-induced prostate enlargement compared with each treatment administered alone.